Falling turnout in British general and local elections has been well documented. But it is not the overall level of turnout that should concern us most. The far greater problem facing British democracy is the growing inequality in turnout, which gives well-off and older voters disproportionate influence at the ballot box.

Electoral participation is falling fastest among the young and the least affluent, resulting in a dramatic social class divide. In the 1987 general election there was only a four-point gap in the turnout rate between the highest income group and the poorest; by 2010 this had jumped to 23 points. The age gap is even more striking. Just 44 per cent of 18-24-year-olds voted in the 2010 general election, compared to 76 per cent of those aged 65 and over, and this 32-point gap has almost doubled from 18 points in 1970.

Unequal turnout matters because it reduces the incentives for governments to respond to the interests of non-voters and thus threatens a central claim of democracy: that every citizen's preference, no matter their status, should count equally. To illustrate the preferential treatment of voters over non-voters, IPPR's analysis of the 2010 spending review shows that those who did not vote in the 2010 general election faced cuts worth 20 per cent of their annual household income, compared to 12 per cent for those who did vote. In this way, unequal turnout unleashes a vicious cycle of disaffection and under-representation among those groups for which participation is falling, for whom politics seems to have less and less to say to them.

This cycle can only be broken by radical measures. In this report, we argue that the best way to boost political participation among hard-to-reach groups is to make voting compulsory. Simple compulsory voting is, however, controversial. A more realistic approach is to make electoral participation compulsory for first-time voters only. These young voters would be compelled only to turn out - and would be provided with a 'none of the above' option on the ballot.

People who vote in their first election are considerably more likely to vote throughout their lives, thereby helping to break the habit of non-voting that often gets passed from generation to generation. It would also go some way toward righting the balance of British electoral politics, which has tilted toward the affluent and 'grey' vote in recent years, as it would force politicians to pay attention to other voter groups.